The three entered, then, the final and largest of the chambers. During the working hours of the day it was a machine shop in which Underlings toiled under the harsh supervision of their Master overseers. Now it was deserted save for rather more than twoscore conspirators similar in physique and coloring to the leader, Sert. Introductions were a brief formality. It was evident that some of the Underlings could not comprehend the anomaly of Sandra and Larry's presence. But what these rebel serfs lacked in intellect they made up for in their lust for freedom. And the two young Americans, hailing from a land that, in its time, had been the bulwark of this precious inheritance, felt a kinship with the suppressed uprisers. At length Sert said, "--so that is as far as our plans have gone, Larry Wilson. You see how pitifully inadequate they are. "Not only do the Masters outnumber us, but theirs is the possession of the golden force-ray which no armament can pierce. None, that is, of the feeble type we own. The force of our greater strength ... tools converted into crude swords...." He looked hopelessly at the massive machinery surrounding them. "Could we but find a way to destroy their protective force-field, we would tear these machines into bits to mold weapons for ourselves. But we cannot." Larry said, "I've been thinking about that problem. And I've got an idea that may or may not work. Sert, it is only the Masters whose ears are sensitive to sound, isn't it? There's nothing wrong with your hearing?" "That is right, Larry Wilson." "Then sound--" began Larry. Sert shook his head. "Do you forget the _menaudo_, my friends? The Masters wear it at all times. It blocks out the sound waves that would torture them, drive them mad." "I haven't forgotten it," grunted Larry. "I'm trying to think of a way to pour sound over 'em without making 'em remove the football helmet. And I think I know how to do it. Strangely enough, you have to make them turn on the golden force-ray before it will work!" "I don't understand," said Sert. Others edged in curiously as Larry explained. "When the force ray surrounds them," he explained, "their bodies become, in effect, a helical core. Such a core can be made responsive to musical tones by what, in my day, we called C.E.M.F.--counter electromotive force. I suppose you know the method of manufacture of the force ray?" "Not the details. But the purely mechanical part, yes. We wind the relays in this shop--" "Then," said Larry crisply, "you've got 'em licked! We'll get to work--_now!_--and build an electrical resonator. One that shoots out plenty of noise on the wave length to which their force-fields are attuned. When this howler gets going, the force-field will act as a conductor, leading the sound directly into their bodies!" Sert's face broke in a huge grin. "And if they turn off the force-field--" he howled.